1. Field of the Invention
The present invention generally relates to hand-held labelling and marking devices for printing information such as prices, etc. on a label material, or alternately directly onto an article. Such devices are most often used in grocery and retail stores for pricing goods and/or labelling goods with an identification number, etc. Such devices for labelling and marking can have a printing mechanism with a number of print wheels or printing belts for carrying the print type. In the case where print wheels are used, the print wheels can preferably be coaxially mounted, whereas, when belts are used, the belts are guided around multiple, coaxial printing area-side guide wheels, or printing-type wheels, of the labelling device. The print wheels, or guide wheels are typically rotationally mounted on a shaft, which shaft is fixed to the housing. In addition, the wheels can also preferably be releasably held in specified rotational positions on the shaft by means of a locking mechanism.
In each specified locking position, the numbers, letters, symbols etc. of all the print wheels and/or printing belts should preferably form exactly one row of print type. The locking mechanism for providing such an alignment can be formed by a number of spring-loaded locking elements, wherein the number of spring loaded locking elements can essentially correspond to the number of print wheels or guide wheels. The locking mechanism can also generally include several locking locators disposed on each of the guide wheels, which locking locators interact with the locking elements. The locking locators are preferably evenly distributed about the bearing hole of the print wheels or guide wheels.
2. Background Information
By means of an adjustment shaft which can be moved axially, and which rotates a printing belt, or print wheel, each print wheel or printing belt can be set, one after the other, with respect to its adjacent wheel or printing belt. Thus, upon completion of an adjustment process for a respective setting of print type, those printing symbols which are to be used to print a label or similar item are in one row. The locking mechanism mentioned above preferably ensures that all of the symbols in the impression form a properly configured row of symbols.
The locking mechanism can also ensure the correct orientation of each symbol with respect to its neighboring symbols for each setting of each print wheel or printing belt. That means that each locking locator of each print wheel, or print-area side guide wheel, essentially must be correctly oriented with respect to the symbols of its print wheel, or the teeth of its guide wheel when viewed circumferentially.
Thus, in the case where printing belts are used, the belts can be designed internally in the form of toothed belts, with the guide wheels forming the associated toothed gears. Also, in the case where print wheels are used, the number of locking locators on the print wheel, for example, can correspond to the number of print symbols on the respective print wheel. By providing a correspondence between locking locators and print symbols, for example, the middle of a toothed symbol carrier can be precisely oriented with the middle of a locking locator. The same applies to the guide wheels in the case of printing belts, but other arrangements are also possible. With printing belts, in particular, one can choose the number of locking locators to be less than the number of teeth on the guide wheels, whereby the number of teeth is preferably a whole multiple of the number of locking locators of the respective wheel. If there are eight teeth, for example, there can be four locking locators at intervals of about 90 degrees. In general, the number of locking locators can essentially be a function of the size of the symbols, seen in the circumferential direction of the belts.
When turning the print wheels or guide wheels on the shaft which is fixed to the housing, which turning in a belt printing mechanism can be accomplished by means of the respective printing belt, the locking element must move radially inward against the resistance of its load spring until the desired rotational orientation of this wheel is reached. At the proper rotational orientation the locking element can be engaged in the associated locking locator.
In a known embodiment of such a printing mechanism, German Patent Publication Published for Opposition Purposes No. 25 37 010, discloses that the locking elements are realized in the form of over-mounted pistons, the inner ends of which are braced against a common flexible strip.
For assembly reasons, each locking element is secured on the shaft against unintentional removal from its locator. This is provided by fixing each locking element to the housing by means of two opposing locking teeth which are engaged in corresponding recesses in the locking element. The engagement of the locking teeth with their locating shaft is accomplished by means of a radial pressure with corresponding elastic guide motions. The barb-like shape of the locking teeth of the shaft which is fixed to the housing prevents the release of this snap-in connection. However, as a result of this coupling of the locking elements with the shaft which is fixed to the housing, the locking elements project at various distances from the shaft so that they are engaged at different depths in the locking locators of the associated wheels. Because of the trapezoidal shape of both the locking locators and the engaging end of the locking elements, engagement at different depths results in a different rotational orientation, which can be reflected by an incorrect row of symbols.